EP0089010B1 - Semikontinuierliches Verfahren zur Herstellung von reinem Silicium - Google Patents

Semikontinuierliches Verfahren zur Herstellung von reinem Silicium Download PDF

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Publication number
EP0089010B1
EP0089010B1 EP83102341A EP83102341A EP0089010B1 EP 0089010 B1 EP0089010 B1 EP 0089010B1 EP 83102341 A EP83102341 A EP 83102341A EP 83102341 A EP83102341 A EP 83102341A EP 0089010 B1 EP0089010 B1 EP 0089010B1
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EP
European Patent Office
Prior art keywords
slag
silicon
aluminum
quartz
reaction
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP83102341A
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German (de)
English (en)
French (fr)
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EP0089010A1 (de
Inventor
Josef Dr.. Dipl.-Phys. Dietl
Claus Dr. Dipl.-Chem. Holm
Jörg Dipl.-Ing. Kotilge
Michael Wohlschläger
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Heliotronic Forschungs- und Entwicklungsgesellschaft fur Solarzellen-Grundstoffe Mbh
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Heliotronic Forschungs- und Entwicklungsgesellschaft fur Solarzellen-Grundstoffe Mbh
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Priority to AT83102341T priority Critical patent/ATE22875T1/de
Publication of EP0089010A1 publication Critical patent/EP0089010A1/de
Application granted granted Critical
Publication of EP0089010B1 publication Critical patent/EP0089010B1/de
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/021—Preparation
    • C01B33/023—Preparation by reduction of silica or free silica-containing material

Definitions

  • the invention relates to a semi-continuous process for the production of pure silicon by reducing quartz with aluminum.
  • Silicon is currently still far too expensive as the basic material for cheap terrestrial solar cells.
  • An important reason for the high price is the previously usual complex cleaning process, according to which the raw silicon initially obtained by reducing quartz with coal is converted into trichlorosilane by the action of hydrogen chloride. This can be purified by distillation and finally decomposed to high-purity polycrystalline silicon in the presence of hydrogen.
  • the silicon obtained in this way then meets the strict purity requirements for electronic components.
  • Such a high level of purity is not required for silicon as the base material for the solar cell, especially if polycrystalline silicon with grain boundaries that get contaminants is used.
  • quartz can be reduced to elemental silicon by aluminum in the presence of an aluminum sulfide slag.
  • the aluminum acts both as a reducing agent for the quartz and as a solvent for the resulting silicon, which can then be crystallized from the solution in an already very pure form by cooling.
  • this process has a high aluminum requirement and requires additional protective measures due to the smell and toxicity of the aluminum sulfide, cf. EP-A-29 182.
  • the invention was therefore based on the object of specifying a process which can be used on an industrial scale and which, based on quartz, allows the production of pure silicon for solar cells while avoiding the expensive gas phase deposition without having the disadvantages of the previously known processes.
  • This object is achieved by a process which is characterized in that a molten alkaline earth silicate slag is placed in a reaction vessel, that batches of quartz and aluminum are introduced into the slag, and that the silicon which forms and separates from the slag is withdrawn in portions from the reaction vessel and that for the regeneration of the slag containing the resulting alumina dissolved, alumina-poor slag material is recharged and a corresponding amount of the slag enriched with alumina is removed from the reaction vessel.
  • a particular advantage of the process according to the invention over the classic arc process is that it is not absolutely necessary to use lumpy quartz, but that even quartz sands, preferably in grain sizes of 0.1 to 5 mm, can advantageously be used. Heavily contaminated quartz sands, although they can in principle also be used directly, are expediently pre-cleaned to a purity of at least 98% by weight of quartz in order to avoid premature overloading of the slag used in the process. However, it is more advantageous to use the quartz sands, which are present in large quantities and have purities of over 99.9%. Numerous silicates, such as kaolinites, various types of mica, feldspars or layered silicates, are also suitable as starting material after suitable chemical and physical processing to give silicon dioxide powder.
  • the aluminum serving as a reducing agent is expediently used in the purest form possible, in order to avoid introducing additional impurities.
  • the use of electrolytically cleaned aluminum with a purity of at least 99.9% has proven particularly useful. If the impurities are substances that accumulate primarily in the slag, even lower levels of purity of the aluminum can be accepted. On the other hand, with regard to impurities that only dissolve slightly in the slag, such as iron or phosphorus, care must be taken from the outset to be as pure as possible.
  • Silicates of the alkaline earth metals magnesium, calcium, strontium and barium which can be used both in pure form and as mixtures of two or more components, have proven to be the most suitable base material for the slag serving as the reaction and extraction medium.
  • the base material for a particularly inexpensive slag for example, cheap calcium silicate is recommended, to which other silicates, such as magnesium silicate, can then be added.
  • the particularly pure barium silicate for example, is particularly suitable for a very pure slag.
  • the slag contains up to 30 mol% Alkaline earth fluorides or other substances which increase the solubility of the aluminum oxide in the slag are added.
  • the alkaline earth silicate slag is initially placed in a reaction vessel which preferably consists of graphite or carbon tamping mass. It can be prepared in a separate vessel and then added in an already molten form, but can also first be brought to the preferred reaction temperature of 1420 to 1600 ° C. in an induction-heated reaction vessel, for example. This temperature range is particularly favorable since the silicon produced is then obtained in the molten form and, on the other hand, side reactions such as e.g. Do not interfere with SiO formation and evaporation of volatile slag components. In principle, however, the choice of higher reaction temperatures is also possible.
  • the quantity of slag presented is expediently chosen to be large enough that the aluminum oxide formed in the first reaction cycle is completely dissolved therein. It is particularly advantageous if the melting temperature of the mixture of slag and aluminum oxide which is formed always remains in the temperature range indicated above, so that solidification of the slag is avoided and it can therefore always be added to a liquid sump.
  • the corresponding proportions and melting temperatures can be found in the associated phase diagrams (see, for example, "Phase Diagrams for Ceramists, The American Ceramic Society, Inc., Volume 1 (1964), Volume 2 (1969), Volume 3 (1975)).
  • the reaction material is now added to the molten slag, which is at the working temperature.
  • quartz and aluminum are premixed in an approximately or exactly stoichiometric ratio and incorporated into the slag in portions. It is advisable to ensure that quartz and aluminum are in a molar ratio of at least 3: 4. Namely, while a small deficit of aluminum has no adverse effects, since the remaining unreacted quartz dissolves in the slag, an excess of aluminum can lead to a reductive attack of the aluminum on the slag, which is unfavorable because of the silicide formation, when all the quartz is used up is. If air is also used, excess aluminum can be oxidized from the atmospheric oxygen to aluminum oxide and is therefore lost as a reducing agent.
  • reaction material in the particularly favorable embodiment of the invention is already weighed out and mixed in a suitable quantitative ratio outside the reaction vessel, it is basically even possible to dispense with stirring when the reaction material is introduced in portions thereafter. Nevertheless, the dissolution of the reaction material in the slag can be improved by using a suitable stirrer, for example a paddle stirrer made of carbon or graphite.
  • a particularly good stirring effect can also be achieved by a perforated plate made of, for example, graphite, which is preferably moved vertically through the reaction mixture.
  • the reaction vessel only needs to be completely externally heated during the start-up phase, i.e. during the melting of the slag and at the start of the reaction.
  • the rate of refilling and the intensity of stirring can be used to design the temperature profile so that the external heating can be largely reduced. Only when the reaction has subsided must heating be increased again in order to prevent the temperature from dropping below the melting point of the reactants and thus preventing the reaction mixture from solidifying.
  • the system is allowed time to separate.
  • the stirrer is stopped and, if necessary, moved out of the reaction mixture, so that the slag begins to settle below in the reaction vessel due to the density ratio.
  • the silicon formed collects on the surface of the slag, whereby it always remains separated from the wall of the reaction vessel by a thin layer of slag.
  • a particular advantage in this connection is that the oxides of the impurities formed on the surface of the silicon formed by reaction with the present atmosphere, for example atmospheric oxygen, are excellently dissolved in the surrounding slag. For this reason, it is not absolutely necessary to carry out the method according to the invention under vacuum or protective gas in a closed system. Particularly good results are achieved even in an open system with air access.
  • the silicon formed is withdrawn from the reaction vessel.
  • a drainage system such as a drainpipe extending from below or laterally into the molten silicon, for example made of graphite.
  • Another elegant possibility is to insert a suitable tube made of, for example, graphite, as a rule from above into the silicon to be removed, and by applying a vacuum Vacuum silicon into another container, where it can then be subjected to directional solidification or vacuum evaporation, for example.
  • the silicon obtained by the process according to the invention is a base material which is particularly well suited for further processing into solar cells.
  • the mixed individual components in the case of a calcium silicate slag, for example calcium oxide and silicon dioxide, but also the corresponding compound, for example calcium silicate or mixtures of calcium silicate, calcium oxide and silicon dioxide, can advantageously be added together with the reaction mixture, but also separately.
  • a calcium silicate slag for example calcium oxide and silicon dioxide
  • the corresponding compound for example calcium silicate or mixtures of calcium silicate, calcium oxide and silicon dioxide
  • An amount of used slag corresponding approximately to the fresh slag addition is removed from the reaction vessel.
  • a drain system is provided in the reaction vessel, which in a particular embodiment of the invention can work, for example, according to the siphon principle.
  • a dividing wall, preferably made of graphite, protruding from the top down into the melt is provided in the reaction vessel, which leaves an opening, generally designed as a gap, above the bottom of the reaction vessel in order to allow the slag to flow through. This means that the same level of slag can build up on both sides of the partition.
  • the gap height so small, for example 5 mm, that only slag, but not silicon, can escape due to the wetting conditions. All silicon remains on one side of the partition, while only slag is found on the other side.
  • a partition made of, for example, graphite can also advantageously be used, which is provided with small holes of approximately 5 mm in diameter and likewise only allows the slag to pass through, but not the silicon.
  • the slag discharge chamber which is separated from the reaction space by the partition, a graphite tube, for example, is provided as the outlet for the slag. It has proven to be particularly favorable if the height of the outlet pipe is adjustable, since the desired height of the slag level can then be set extremely easily in the entire reaction vessel.
  • the used slag flowing out of the slag discharge chamber finally arrives in a slag processing chamber, where it is processed to recover the aluminum oxide contained in solution.
  • the aluminum oxide can be crystallized out by cooling and separated, for example, by filtration using a suitable graphite filter or by centrifugation. Another suitable method is e.g. the deposition of the aluminum oxide on cooled plates made of, for example, graphite, which are immersed in the molten slag.
  • the aluminum oxide content of the used slag is up to 60% by weight, preferably 35 to 50% by weight, prior to processing.
  • the separated aluminum oxide is finally subjected to the reduction, that is to say, for example, the classical melt electrolysis in molten cryolite, in order to recover aluminum.
  • the resulting pure aluminum can then be reintroduced into the reaction cycle.
  • the cycle process is again shown schematically for better clarification:
  • a molten slag 2 made of alkaline earth silicates is placed in the reaction vessel 1.
  • the reaction mixture 4 made of quartz and aluminum is added to this slag from a storage vessel 3.
  • the silicon 5 formed has separated from the slag and can be discharged into the mold 8 via a drain pipe 6 with flow regulator 7 and further treated.
  • part of the used slag is now displaced into the slag discharge chamber 10, which is divided off by a partition 9, from where it flows out into the slag preparation chamber 12 via a drain pipe 11.
  • the aluminum oxide dissolved in the slag is separated off and fed to the melt electrolysis 13, from which recovered aluminum is added to the reaction mixture 4 again.
  • the silicon obtained and the starting materials had the following impurities (data in ppm by weight):
  • the silicon obtained and the starting materials had the following impurities (data in ppm by weight):

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Silicon Compounds (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Glass Compositions (AREA)
  • Physical Deposition Of Substances That Are Components Of Semiconductor Devices (AREA)
  • Saccharide Compounds (AREA)
EP83102341A 1982-03-11 1983-03-10 Semikontinuierliches Verfahren zur Herstellung von reinem Silicium Expired EP0089010B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83102341T ATE22875T1 (de) 1982-03-11 1983-03-10 Semikontinuierliches verfahren zur herstellung von reinem silicium.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19823208878 DE3208878A1 (de) 1982-03-11 1982-03-11 Semikontinuierliches verfahren zur herstellung von reinem silicium
DE3208878 1982-03-11

Publications (2)

Publication Number Publication Date
EP0089010A1 EP0089010A1 (de) 1983-09-21
EP0089010B1 true EP0089010B1 (de) 1986-10-15

Family

ID=6157973

Family Applications (1)

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EP83102341A Expired EP0089010B1 (de) 1982-03-11 1983-03-10 Semikontinuierliches Verfahren zur Herstellung von reinem Silicium

Country Status (9)

Country Link
US (1) US4457903A (es)
EP (1) EP0089010B1 (es)
JP (1) JPS58156520A (es)
AT (1) ATE22875T1 (es)
AU (1) AU563532B2 (es)
CA (1) CA1194679A (es)
DE (2) DE3208878A1 (es)
ES (1) ES8308807A1 (es)
NO (1) NO158868C (es)

Families Citing this family (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3208877A1 (de) * 1982-03-11 1983-09-22 Heliotronic Forschungs- und Entwicklungsgesellschaft für Solarzellen-Grundstoffe mbH, 8263 Burghausen Verfahren zur entfernung des schlackenanteils aus schmelzmischungen von schlacke und silicium
US4798659A (en) * 1986-12-22 1989-01-17 Dow Corning Corporation Addition of calcium compounds to the carbothermic reduction of silica
NO316020B1 (no) * 2001-10-10 2003-12-01 Elkem Materials Anordning for kontinuerlig slaggbehandling av silisium
NO318092B1 (no) * 2002-05-22 2005-01-31 Elkem Materials Kalsium-silikatbasert slagg, fremgangsmate for fremstilling av kalsium-silikatbasert slagg, og anvendelse for slaggbehandling av smeltet silium
WO2004101434A1 (en) * 2003-05-15 2004-11-25 Helmut Engel The metallurgical method of receiving the high purity silicon powder by chemical processing
EA009888B1 (ru) * 2004-10-12 2008-04-28 Министерство Образования И Науки Республики Казахстан Республиканское Государственное Предприятие "Центр Химико-Технологических Исследований" Дочернее Государственное Предприятие "Физико-Технический Институт" Способ получения чистого кремния
JP4966560B2 (ja) * 2005-03-07 2012-07-04 新日鉄マテリアルズ株式会社 高純度シリコンの製造方法
JP4845480B2 (ja) * 2005-03-28 2011-12-28 京セラ株式会社 半導体インゴット製造装置及び半導体インゴットの製造方法
JP2007204353A (ja) * 2006-02-06 2007-08-16 Univ Of Tsukuba シリコン結晶析出方法及びシリコン結晶材料
JP4997053B2 (ja) * 2007-10-02 2012-08-08 日立造船株式会社 高純度シリコンの製造方法
KR20130063501A (ko) 2010-05-20 2013-06-14 다우 코닝 코포레이션 알루미늄-규소 합금을 생성하기 위한 방법 및 시스템
WO2012000428A1 (en) * 2010-06-29 2012-01-05 Byd Company Limited Method for preparing high purity silicon
KR101306688B1 (ko) 2012-04-17 2013-09-17 연세대학교 산학협력단 슬래그로부터 실리콘을 회수하는 방법 및 장치
EA029631B1 (ru) * 2016-09-15 2018-04-30 Геннадий Николаевич Чумиков Способ получения металлургического кремния повышенной чистоты из кремнийсодержащих полупродуктов (кварцевая мелочь, пыль кремниевого производства (микрокремнезем)) методом алюминотермии
GB201621609D0 (en) 2016-12-19 2017-02-01 Norwegian Univ Of Science And Tech (Ntnu) Process for the production of commercial grade silicon
RU2690877C1 (ru) * 2018-09-27 2019-06-06 Федеральное государственное бюджетное образовательное учреждение высшего образования "Сибирский государственный индустриальный университет", ФГБОУ ВО "СибГИУ" Способ выделения металлического кремния из шлака технического кремния
EP3643680A1 (en) 2018-10-23 2020-04-29 SiQAl UG (haftungsbeschränkt) Coupled production of high purity silicon and alumina

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2904405A (en) * 1957-10-31 1959-09-15 Bell Telephone Labor Inc Recovery of silicon from silicon dioxide
US3322503A (en) * 1964-05-20 1967-05-30 Bloom Harry Silicon production process
US3871872A (en) * 1973-05-30 1975-03-18 Union Carbide Corp Method for promoting metallurgical reactions in molten metal
DE2706175C3 (de) * 1977-02-14 1980-05-29 Wacker-Chemie Gmbh, 8000 Muenchen Verfahren zum Verschmelzen und Reinigen von Silicium
US4124410A (en) * 1977-11-21 1978-11-07 Union Carbide Corporation Silicon solar cells with low-cost substrates
DE2933164A1 (de) * 1979-08-16 1981-02-26 Consortium Elektrochem Ind Verfahren zum reinigen von rohsilicium
DE2945070A1 (de) * 1979-11-08 1981-06-04 Heliotronic Forschungs- und Entwicklungsgesellschaft für Solarzellen-Grundstoffe mbH, 8263 Burghausen Semikontinuierliches verfahren zur herstellung von reinem silicium

Also Published As

Publication number Publication date
ES518315A0 (es) 1983-10-01
ATE22875T1 (de) 1986-11-15
NO158868C (no) 1988-11-09
US4457903A (en) 1984-07-03
JPS6126491B2 (es) 1986-06-20
AU1196683A (en) 1983-09-15
DE3208878A1 (de) 1983-09-22
AU563532B2 (en) 1987-07-16
EP0089010A1 (de) 1983-09-21
NO158868B (no) 1988-08-01
ES8308807A1 (es) 1983-10-01
CA1194679A (en) 1985-10-08
DE3366905D1 (en) 1986-11-20
NO830842L (no) 1983-09-12
JPS58156520A (ja) 1983-09-17

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